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At least 919 records · Page 51Linked to original sources
PubMed2006

Heat and moisture exchangers and heated humidifiers in acute lung injury/acute respiratory distress syndrome patients. Effects on respiratory mechanics and gas exchange.

OBJECTIVE: To compare, in acute lung injury/acute respiratory distress syndrome (ALI/ARDS) patients, the short-term effects of heat and moisture exchangers (HME) and heated humidifiers (HH) on gas exchange, and also on respiratory system mechanics when isocapnic conditions are met. DESIGN: Prospective open clinical study. SETTING: Intensive Care Service. PATIENTS: Seventeen invasively ventilated ALI/ARDS patients. INTERVENTION: The study was performed in three phases: (1) determinations were made during basal ventilatory settings with HME; (2) basal ventilatory settings were maintained and HME was replaced by an HH; (3) using the same HH, tidal volume (Vt) was decreased until basal PaCO2 levels were reached. FiO2, respiratory rate and PEEP were kept unchanged. MEASUREMENTS AND RESULTS: Respiratory mechanics, Vdphys, gas exchange and hemodynamic parameters were obtained at each phase. By using HH instead of HME and without changing Vt, PaCO2 decreased from 46+/-9 to 40+/-8 mmHg (p<0.001) and Vdphys decreased from 352+/-63 to 310+/-74 ml (p<0.001). Comparing the first phase with the third, Vt decreased from 521+/-106 to 440+/-118 ml (p<0.001) without significant changes in PaCO2, Vd/Vt decreased from 0.69+/-0.11 to 0.62+/-0.12 (p<0.001), plateau airway pressure decreased from 25+/-6 to 21+/-6 cmH2O (p<0.001) and respiratory system compliance improved from 35+/-12 to 42+/-15 ml/cmH2O (p<0.001). PaO2 remained unchanged in the three phases. CONCLUSIONS: Reducing dead space with the use of HH decreases PaCO2 and more importantly, if isocapnic conditions are maintained by reducing Vt, this strategy improves respiratory system compliance and reduces plateau airway pressure.

Adult↗
PubMed2003

Heat distribution and heat transport in bone during radiofrequency catheter ablation.

BACKGROUND: To assess the feasibility of percutaneous radiofrequency ablation in large bone tumours, the heat distribution in cortical bone and marrow around inserted electrodes was measured. METHODS: Fresh bovine cadaver tibial bones were locally heated through drill holes for a maximum of half an hour using water-cooled single radiofrequency electrodes (Radionics Instruments Inc) by pulsed energy. Temperatures were measured in the marrow canal as well as in cortical bone by thermocouples at various distances from the inserted probes. RESULTS: Perpendicular to the probe, hyperthermia of more than 50 degrees C could be created in bone marrow in a sphere of approximately 3 cm, and of approximately 1 cm in cortical bone. CONCLUSION: As irreversible cellular damage can be expected when increasing the temperature to 50 degrees C for a duration of 6 min, this method may be effective for the minimal invasive ablation of neoplasms within human bone in cigar-shaped regions of approximately 3-cm diameter.

Animals↗
PubMed2005

Effects of physical training on heat loss responses of young women to passive heating in relation to menstrual cycle.

To examine the effects of physical training on cutaneous vasodilation and sweating responses of young women in the follicular and luteal phase, 11 physically trained (T group) and 13 untrained (U group) women were passively heated by lower-leg immersion into hot water of 42 degrees C (ambient temperature of 30 degrees C and 45%RH) for 60 min in their mid-follicular and mid-luteal phases of the menstrual cycle. Female hormones increased significantly from the mid-follicular to the mid-luteal phase in T and U groups, but the degree of increase was significantly lower in T group. Mean body temperature (T(B)) thresholds for cutaneous vasodilation and sweating responses were significantly lower in T group than in U group, in both the menstrual phases, and the differences between the groups were greatest during the mid-luteal phase. The slope of the relationship between frequency of sweat expulsion (F(sw)) and (T(B)), and between local sweating rate and F(sw) was significantly greater in T group, although the slope of the relationship between cutaneous blood flow and (T(B)) did not differ between the groups, regardless of body site or menstrual phase. These results suggest that regular physical activity enhanced sweating and cutaneous vasodilation in young women. The enhancement of sweating was due to both central and peripheral mechanisms, and the enhancement of cutaneous vasodilation was possibly due to a central mechanism. Enhancement of heat loss responses via central mechanisms was greater during the mid-luteal phase than in the mid-follicular phase because the elevation of female reproductive hormone levels during the mid-luteal phase was relatively low in T group.

Body Temperature Regulation↗
PubMed2000

Peripheral computed tomography (pQCT) detected short-term effect of AAACa (heated oyster shell with heated algal ingredient HAI): a double-blind comparison with CaCO3 and placebo.

Trabecular bone density at the distal radius and cortical bone density at the midradius were measured in four randomized groups of women before and after 4 months administration of AAACa, oyster shell heated under reduced pressure with addition of heated algal ingredient (HAI) (group A); AACa, the same preparation without HAI (group B); CaCO3 (group C); and placebo (group D) in a double-blind system using peripheral quantitative computed tomography (pQCT) with lumbar spine density measurement by dual-energy X-ray absorptiometry (DXA). Groups A, B, and C received 900 mg/day elemental calcium and D received none. In subjects of group A, but not B, C, and D, radial trabecular bone density increased significantly, to 106.2% +/- 2.1% of the initial value (mean +/- SEM). The increase of trabecular bone density was significantly different from the placebo group (D) only in AAACa (group A) and not in AACa (group B) and the calcium carbonate (group C). Cortical bone density increase was also greater in group A (but not in B and C) than in D. Lumbar spine density did not change significantly. AAACa was apparently more effective, increasing trabecular bone density more than AACa and CaCO3 containing the same amount of elemental calcium.

Absorptiometry, Photon↗
PubMed1990

Differences between the mechanisms of action of heat-stable and heat-labile enterotoxins of Escherichia coli.

The mucosal-to-serosal and serosal-to-mucosal fluxes of Na+ and Cl- were measured in control mice and mice treated with heat-stable (ST) and heat-labile (LT) enterotoxins in the presence or absence of: Ca2(+)-ionophore A23187, an activator of Ca2(+)-calmodulin; or phorbol-12-myristate-13-acetate (PMA), an activator of protein kinase C(PKC); or 1-(5-isoquinolinyl sulphonyl)-2-methyl piperazine (H-7), an inhibitor of PKC. There was net secretion of Na+ and CL- in both experimental groups in contrast to net absorption in the control group. The addition of ionophore or PMA or ionophore + PMA resulted in net secretion of Na+ and Cl- in the control group and the effect of ionophore and pMA was found to be additive. The addition of ionophore did not cause any change in electrolyte fluxes in the ST toxin treated group, however, it increased the net secretion of Na+ and Cl- in the LT toxin treated group. PMA increased the net secretion of Na+ and Cl- in the St toxin treated group, however, it did not cause any change in Na+ and Cl- fluxes in the LT toxin treated group. H-7 did not reverse the effect of ST toxin, however, it reversed the effect of LT toxin.(ABSTRACT TRUNCATED AT 250 WORDS)

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1989

Nucleotide sequences of genes encoding heat-stable and heat-labile glyceraldehyde-3-phosphate dehydrogenases; amino acid sequence and protein thermostability.

The structural gene (gapST) encoding glyceraldehyde-3-phosphate dehydrogenase (GPDH; EC 1.2.1.12) from Bacillus stearothermophilus has been cloned in Escherichia coli using plasmid pBR322 as a vector; the homologous gene (gapCO) from Bacillus coagulans was cloned from a phage lambda library. Expression of the cloned gap genes revealed that, as in the wild-type (wt) organisms, the GPDH from B. stearothermophilus (GPDH-ST) was intrinsically heat stable (hs) and that from B. coagulans (GPDH-CO) heat labile (hl). The cloned gap genes were sequenced and the deduced amino acid (aa) sequences were found to be highly conserved (91.6% homology), despite the large difference in thermostability between these two enzymes. Of the 28 aa which differ between the two proteins, most of which occur in the middle third of the monomeric subunit, 5 aa involve replacement of alanine in the hl GPDH-CO, by proline in the hs GPDH-ST, and are especially interesting in terms of their potential contributions to thermostability. Conservation at the DNA level is equally dramatic, with the two gap genes exhibiting 93.3% nucleotide sequence homology. These highly expressed genes exhibit an equivalent codon bias, which more closely resembles that of highly expressed E. coli genes, than that of B. stearothermophilus genes whether highly or weakly expressed.

Amino Acid Sequence↗
PubMedDate not supplied

Do heated humidifiers and heat and moisture exchangers prevent temperature drop during lower abdominal surgery?

STUDY OBJECTIVE: To compare the effects of using a heated humidifier (HH), a heat and moisture exchanger (HME), or no warming device in maintaining body temperature during surgical procedures of 1 to 4 hours' duration. DESIGN: A randomized, controlled study. SETTING: Operating room, Thomas Jefferson University Hospital, Philadelphia, PA. PATIENTS: 51 ASA physical status I, II, and III patients, age 16 to 69 years, scheduled for a variety of lower abdominal procedures under general endotracheal anesthesia anticipated to last 1 to 4 hours. INTERVENTIONS: We randomly assigned patients to receiving an HH, an HME, or no warming device during the procedure. We then measured the patient's sublingual temperature every 5 minutes prior to induction, every 15 minutes intraoperatively, and every 15 minutes postoperatively until he or she was discharged from the postanesthesia care unit, (PACU). We also measured the esophageal temperature every 15 minutes intraoperatively. MEASUREMENTS AND MAIN RESULTS: Sublingual temperature or esophageal temperature probes placed at the site of maximal heart tones indicated that the patients' temperatures dropped significantly from baseline values in all three groups during the first 60 minutes of surgery, then remained constant during the next 120 minutes of surgery. Patients who had no warming device shivered and felt cold significantly more often than patients in the HH group but not more often than patients in the HME group. There was no difference in shivering between the HH and HME groups. The patients who received an HH tended to have a higher temperature (a mean of 0.5 degrees C) throughout the study, but this did not reach statistical significance. CONCLUSIONS: Results indicate that these warming devices provide little benefit in preventing a temperature drop during procedures of 1 to 4 hours' duration, although patients with an HH tended to have a higher temperature than those with an HME or no device.

Abdomen↗
PubMed2006

In vivo expression of the heat stable (estA) and heat labile (eltB) toxin genes of enterotoxigenic Escherichia coli (ETEC).

Enterotoxigenic Escherichia coli (ETEC) colonize the intestine and adhere to the epithelium by means of different host specific colonization factors (CFs). Colonizing ETEC produce one or both of two enterotoxins; the heat stable (ST) and heat labile (LT) toxins which are both able to cause diarrhoea. The regulation of virulence genes in ETEC during infection of the human intestine is mainly unknown. In this study we analysed the level of mRNA expression of estA, coding for ST, and eltB, coding for the B subunit of LT, during human infection. The expressions of the toxins in ETEC strains expressing both ST and LT were investigated in bacteria isolated directly from patient stool without sub-culturing, (in vivo) and compared to the expression pattern of the corresponding ST/LT strains grown in liquid broth (in vitro) by quantitative competitive RT-PCR using fluorescent primers. We found that estA and eltB are expressed in the in vivo samples but no significant up-or down regulation of the expression levels of either estA or eltB could be determined in vivo as compared to in vitro.

Adaptation, Physiological↗
PubMed2006

Rapid and sensitive detection of heat-labile I and heat-stable I enterotoxin genes of enterotoxigenic Escherichia coli by Loop-Mediated Isothermal Amplification.

We developed a technique for detecting the heat-labile I (LTI) and heat-stable I (STI) genes of enterotoxigenic Escherichia coli (ETEC) using a novel DNA amplification procedure designated Loop-Mediated Isothermal Amplification (LAMP). The detection limit of accelerated LAMP utilizing loop primers was 4 CFU/test for LTI and was 40 CFU/test for STI, which are 10-fold higher than those of conventional PCR assay (detection limit, 40 CFU/test and 400 CFU/test, respectively). No DNA amplification was observed in LT and ST non-producing E. coli or other bacterial strains; thus, high specificity was verified. The specificity of LAMP assay was also confirmed by digestion of LAMP products using restriction enzymes and DNA sequence analysis. In the accelerated LAMP assay, DNA amplification was detected within 35 min, and thus LAMP is superior to conventional PCR in terms of rapidity. It was confirmed that increased concentrations of primers and Bst DNA polymerase could further facilitate the reaction. Furthermore, with the high amplification efficiency of the LAMP assay, amplification can be visually observed by the turbidity caused by magnesium pyrophosphate, a byproduct of the reaction. Detection of LTI and STI in ETEC by LAMP is thus an extremely rapid procedure with high sensitivity and specificity that requires no specialized equipment. This assay is expected to become a valuable tool for rapid diagnosis in ETEC infection.

Bacterial Toxins↗
PubMed2004

Intracerebroventricular tryptophan increases heating and heat storage rate in exercising rats.

The role of increased hypothalamic tryptophan (TRP) availability on thermoregulation and rates of core temperature increase and heat storage (HS) during exercise was studied in normal untrained rats running until fatigue. The rats were each anesthetized with 2.5% tribromoethanol (1.0 ml kg(-1) ip) and fitted with a chronic guiding cannula attached to the right lateral cerebral ventricle 1 week prior to the experiments. Immediately before exercise, they were randomly injected through these cannulae with 2.0 microl of 0.15 M NaCl (SAL; n=6) or 20.3 microM L-TRP solution (n=7). Exercise consisted of running on a treadmill at 18 m min(-1) and 5% inclination until fatigue. Body temperature was recorded before and during exercise with a thermistor probe implanted into the peritoneal area. Rates of core temperature increase (HR, degrees C min(-1)) and heat storage (HSR, cal min(-1)) were calculated. TRP-treated rats showed a rapid increase in body temperature which was faster than that observed in the saline-treated group during the exercise period. The TRP group also showed a higher rate of core temperature increase and HS. TRP-treated rats that presented higher HR and HSR also fatigued much earlier than saline-treated animals (16.8+/-1.1 min TRP vs. 40+/-3 min SAL). This suggests that the reduced running performance observed in TRP-treated rats is related to increased HR and HSR induced by intracerebroventricular injection of TRP in these animals.

Animals↗
PubMed1978

Escherichia coli strains that cause diarrhoea but do not produce heat-labile or heat-stable enterotoxins and are non-invasive.

Three enteropathogenic Escherichia coli (E.P.E.C.) strains (O127:K63:H6, O128:K67:H2, and O142:K86:H6) isolated from outbreaks of infantile diarrhoea and one strain from the "normal" colonic flora (E. coli HS) of a healthy adult were fed in doses of 10(6), 10(8), and 10(10) organisms in NaHCO3 to adult volunteers. The strains, which had been stored for 7--9 years, gave negative results in sensitive tests for heat-labile (L.T.) enterotoxin (Y-1 adrenal-cell test), heat-stable (S.T.) enterotoxin (infant mouse assay), invasiveness (guineapig eye test), and gross fluid accumulation (infant rabbit assay). Two strains (O142 and O127) caused diarrhoea. L.T. or S.T. enterotoxins were not found in E. coli stool isolates from individuals with diarrhoea and no one had a rise in L.T. antitoxin titre; the findings suggest that L.T. and S.T. enterotoxins were not involved in pathogenesis of the diarrhoea. Non-invasive E.P.E.C. strains probably induce diarrhoea by a mechanism (presumably an enterotoxin) distinct from L.T. or S.T. enterotoxins.

Adult↗
PubMed2000

Comparison of finite element and heated disc models of tissue heating by ultrasound.

This paper compares different techniques used to model the heating caused by ultrasound (US) in a phantom containing a layer of bone mimic covered by agar gel. Results from finite element (FE) models are compared with those from two techniques based on the point-source solution to the bioheat transfer equation (BHTE): one in which the bone mimic is considered to be an absorbing disc of infinitesimal thickness and the other in which the region through which the US travels is considered to be a volume heat source. The FE results are also compared with experimental measurements. The results from the models differed by up to 40% compared with those from the FE model. Furthermore, for the intensity distribution considered, which corresponds to that in the focal zone of a single-element transducer, the top hat distribution predicts a temperature rise 1.8 times greater than that for a more realistic one based on measured values.

Agar↗
PubMed1999

Determination of nerve conduction velocity of C-fibres in humans from thermal thresholds to contact heat (thermode) and from evoked brain potentials to radiant heat (CO2 laser).

This study was designed to estimate and compare nerve conduction velocity (NCV) of cutaneous heat-sensitive C-fibres obtained using two methods. The first is a method based on reaction times to different rates of temperature change produced by a large contact thermode (Thermotest). The second is a novel method based on ultra-late-evoked brain potentials to CO2 laser stimuli with tiny beam sections (< 0.25 mm2), allowing selective and direct activation of very slow conducting afferents. Both methods were applied on three sites of the right leg (foot, knee and thigh) of ten healthy subjects. When based on the reaction times to contact heat, NCV estimations were 0.4 +/- 0.22 m/s for the proximal segment (knee-thigh) and 0.6 +/- 0.23 m/s for the distal segment (foot-knee). When based on the difference in latency of the ultra-late positivity of laser-evoked brain potentials, NCV estimations were respectively 1.4 +/- 0.77 m/s and 1.2 +/- 0.55 m/s. For both methods, the difference in NCV between proximal and distal limb segments was not significant. Although both methods give NCV estimations within the range of C-fibres, the systematic difference between NCV obtained from each method may result from the activation of subpopulations of C-fibres with different NCV depending on the method of stimulation (low-threshold thermal receptors by the thermode and thermal nociceptors by the CO2 laser). Considering the difficulty of investigating peripheral fibres with slow conduction velocities (C-fibres) in humans, the methods used in the present study may be useful tools in both experimental and clinical situations.

Adult↗
PubMed2000

Characteristic thermal constant and dimensionless heating rate. The links to optimum heating rate in GC

An initial step in the quest of deriving a generalized approach to optimization of a temperature program in gas chromatography is presented. Central to this is the introduction of a dimensionless heating rate, r. As a first step to defining r, a characteristic thermal constant, thetachar, defined as thetachar = -dT/dk at k = 1, where T and k are, respectively, column temperature and solute retention factor, is introduced and evaluated for our own experimental data and for thermodynamic data from the literature. It was determined that, for silicone stationary phases with a phase ratio of 250, thetachar ranged from about 23 degrees C for low molecular weight hydrocarbons such as dimethylpropane to about 45 degrees C for high molecular weight pesticides such as mirex. It was also found that, for a particular solute and a stationary phase type, a 2 orders of magnitude increase in the film thickness caused only about a 2-fold increase in the characteristic thermal constant. Using thetachar as a fundamental temperature unit in GC and void time as a fundamental time unit, a dimensionless heating rate is introduced and its potential utility for the evaluation of the separation-speed tradeoffs in a temperature-programmed GC is demonstrated.

Journal Article↗
PubMed2006

Heat markers and quality indexes of industrially heat-treated [15N] milk protein measured in rats.

To determine the bioavailability of industrially heat-treated milk proteins, male Wistar rats were given [15N]-labeled meals containing either nonheated-micellar casein (CAS), milk soluble protein isolate (MSPI), and microfiltered milk (MF)-or heated products-"high temperature short time" pasteurized (HTST), "higher temperature, shorter time" pasteurized (HHST), ultrahigh temperature-treated (UHT), and spray-dried (SPRAY) milks. The postprandial distribution of dietary nitrogen was measured in the splanchnic area and urea. Digestibility was around 96% except for SPRAY (94%) and MSPI (98%). Ingested nitrogen recovered in the splanchnic bed was 19.3% for SPRAY, 16.7% for MF, and around 14-15% for other products. Deamination of dietary nitrogen reached 21.2, 20.6, and 18.2% of ingested nitrogen for MSPI, SPRAY, and CAS, respectively, and around 14-16% for other products. In our model, only spray drying led to a significant increase of splanchnic extraction. Moreover, the biological value of purified protein fractions appeared to be lower than that seen in products containing total milk protein.

Animals↗
PubMed2001

Does the chloroplast small heat shock protein protect photosystem II during heat stress in vitro?

It has been suggested that the function of the chloroplast-localized small heat shock protein (sHsp) is to protect photosystem II (PSII) from heat inactivation. This paper reports that addition of purified sHsp protein to isolated thylakoid membranes gave no protection of PSII and questions that there is any direct effect of the sHsp on PSII. The opinion is forwarded that the primary role for the chloroplast-localized sHsp may not even be protection of PSII.

Journal Article↗
PubMed1998

Development and use of a multiplex PCR system for the rapid screening of heat labile toxin I, heat stable toxin II and shiga-like toxin I and II genes of Escherichia coli in water.

Enterotoxigenic Escherichia coli (ETEC) may produce heat-labile toxin (LT) I and LTII and heat-stable toxin (ST) I and STII, while shiga toxin producing E. coli (STEC) strains, including enterohaemorrhagic E. coli (EHEC), may produce shiga-like toxin (SLT) I and/or SLTII. Both ETEC and STEC are pathogenic to humans, pigs and cattle. As contamination of environmental water by any of these pathogenic E. coli cells is possible, a multiplex polymerase chain reaction (PCR) system for the rapid screening of LTI, STII, and SLTI and SLTII genes of E. coli was developed. The PCR primers used were the SLTI and SLTII genes specific primers developed by the present authors and the LTI and STII genes specific primers reported by other laboratories. The detection specificity of this multiplex PCR system was confirmed by PCR assay of ETEC, STEC and other E. coli cells as well as non-E. coli bacteria. Its detection limit was 10(2)-10(3) cfu each of the target cells per assay. When this multiplex PCR system was used for the rapid screening of LTI, STII ETEC and STEC in water samples such as tap, underground and lake waters, it was found that after the enrichment step, as few as 10(0) cells 100 ml-1 of the water sample could be detected. Therefore, this PCR system could be used for the rapid monitoring of ETEC and/or STEC cells contaminating water samples.

Animals↗
PubMed1978

Metabolism of heat-damaged proteins in the rat. Inhibition of amino acid uptake by "unavailable peptides" isolated from enzymic digests of heat-damaged cod fillet.

1. An extract containing "unavailable" small peptides was isolated from an enzymic digest of heat-damaged cod fillet and examined for its influence on uptake of leucine in the rat small intestine, using the everted-sac technique. 2. The extract strongly inhibited the uptake of leucine. It had no effect on uptake of glucose or its metabolism to lactate. 3. The findings are discussed in relation to the concept (Buraczewski, Buraczewska & Ford, 1967) that the accumulation of "unavailable peptide" material in the intestine, found in rats given heat-damaged protein, might hinder the absorption of amino acids by blocking a mechanism involved in their transport across the mucosal barrier.

Animals↗